One of the questions I’m asked most often at The Incidental Economist blog, on my YouTube channel, and through other means of communication is whether vitamin D supplementation is a good thing. I’m amazed at the persistence of this question, as study after study seems to show that vitamin D isn’t doing most of us much good at all.

In a recent issue of JAMA, researchers tested whether 2 years of taking supplemental vitamin D might help patients with symptomatic osteoarthritis of the knee. The main outcomes of interest involved measurements of tibial cartilage volume, pain scores, cartilage defects, and bone marrow lesions. After the study period, there were no significant improvements in any of these outcomes. There were, however, significantly more adverse events in those taking the vitamin D.

Last October, JAMA Internal Medicine published a randomized, controlled trial of vitamin D examining its effects on musculoskeletal health. Postmenopausal women were given either the supplement or placebo for one year. Measurements included total fractional calcium absorption, bone mineral density, muscle mass, fitness tests, functional status, and physical activity. On almost no measures did vitamin D make a difference.

The accompanying editor’s note observed that the data provided no support for the use of any dose of vitamin D for bone or muscle health.

Last year, also in JAMA Internal Medicine, a randomized controlled trial examined whether exercise and vitamin D supplementation might reduce falls and falls resulting in injury among elderly women. Its robust factorial design allowed for the examination of the independent and joined effectiveness of these 2 interventions. Exercise reduced the rate of injuries, but vitamin D did nothing to reduce either falls or injuries from falls.

In the same issue, a systematic review and meta-analysis looked at whether evidence supports the contention that vitamin D can improve hypertension. A total of 46 randomized, placebo controlled trials were included in the analysis. At the trial level, at the individual patient level, and even in subgroup analyses, vitamin D was ineffective in lowering blood pressure.

A recent study by US researchers and another by Danish researchers found that vitamin D supplementation during pregnancy didn’t prevent asthma in young offspring.

A Cochrane review found it unlikely that vitamin D can help treat chronic pain, although many people still try. Another found that vitamin D supplementation decreases cancer occurrence in elderly people. A Lancet meta-analysis argued that “continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate.”

One Cochrane review from 2012 found that vitamin D3, but not vitamin D2, alfacalcidol, or calcitriol, decreased mortality in women older than 70 years who were in institutions or under dependent care. But 150 such women had to be treated for 5 years to prevent 1 death.

Few would argue that people who are deficient in vitamins, including vitamin D, should not be supplemented. But screening turns up so few truly deficient people that the US Preventive Services Task Force does not recommend screening widely for it. Yet millions of people take vitamin D every day.

Vitamin D supplementation is just the tip of the iceberg, though. We spent $21 billion in the United States on vitamins and herbal supplements in 2015 alone, and it’s likely that the vast majority of that is doing us no good.

That may seem like chump change in the scheme of health care spending. But it’s indicative of a larger problem in our health care system. We are willing to spend vast amounts of money on things that we have found don’t work when we study them. Whether these are surgical procedures that have been proven no better than sham surgery in controlled trials, screening that seems less and less effective, or drugs with little or no proven benefit.

TheChoosing Wiselycampaign is premised on the idea that there are many, many things we do in medicine that we shouldn’t. Almost all of them cost money.

Too often, when confronted with the massive cost of health care in the United States, we throw up our hands in despair, as if there’s nothing we can do to stem the tide without negatively affecting health. That’s untrue. There’s billions of dollars in wasteful medical spending that could be cut with no negative effect on outcomes. Unfortunately, too many people think of that waste as “care.”

Ending that spending will be unpopular in the short run. Many will likely call it “rationing.” But in this election season, as politicians cast around looking for ways to reduce the cost of our health care in a way that maintains or improves quality, it’s a good place to start.

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About the author: Aaron E. Carroll, MD, MS, is a health services researcher and the Vice Chair for Health Policy and Outcomes Research in the Department of Pediatrics at Indiana University School of Medicine. He blogs about health policy at The Incidental Economist and tweets at @aaronecarroll.

About The JAMA Forum:JAMA has assembled a team of leading scholars, including health economists, health policy experts, and legal scholars, to provide expert commentary and insight into news that involves the intersection of health policy and politics, economics, and the law. Each JAMA Forum entry expresses the opinions of the author but does not necessarily reflect the views or opinions of JAMA, the editorial staff, or the American Medical Association. More information is available here and here.